Piston assembly



Oct. 5, 1954 J. CALLING ET AL 2,690,940

PISTON ASSEMBLY Original Filed July 13, 1949 2 Sheds-Sheet l fziz Oct.5, 1954 J. CALLING ET AL PISTON ASSEMBLY 2 Sheets-Sheet 2 Original FiledJuly 13, 1949 fizz/627%; 1/032 62 2/??? 1312-22222? 55059 Patented Oct.5, 1954 UNITED STATES ATENT OFFICE PISTON ASSEMBLY John Calling andWilliam F. Borgerd, Evansville,

Ind., assignors to International Harvester Company, a corporation of NewJersey 4 Claims.

This invention relates to an improved piston assembly for compressorsand the like. More particularly it relates to a piston and a novelwrist-pin carrier construction and the improved connection between theparts. The present application is a division of applicant's co-pendingapplication, Serial No. 104,526, filed July 13, 1949, for Connecting Rodand Piston Assembly.

The conventional piston assembly generally comprises a piston having ahead portion and a cylindrical skirt portion which has alignedtransverse openings to provide Wrist-pin bearings. A wrist-pin has itsends journalled in the wrist-pin bearings and a connecting rod isusually keyed to the Wrist-pin intermediate its ends. In the case of acompressor or pump the connecting rod receives power from a rotatablecrank shaft and transmits the power to the piston by way of thewrist-pin. The piston then compresses the gas or other fluid within thecylinder to, a desired pressure.

Heretofore, it was necessary to employ elaborate means to obtain a highvolumetric efficiency because the compressed gas has a tendency to leakbetween the piston and cylinder thereby reducing the ratio of the actualgas pumped with respect to the volume swept by the piston during itstravel in the cylinder. Since the conventional piston has wrist-pinbearing openings in the piston skirt, the compressor efficiency, whichis directly related to volumetric efficiency, is decreased by the escapeof compressed gases from within the cylinder, through the wrist-pinbearing openings, to the crankcase. With this factor in mind, compressormanufacturers have increased the length of the piston skirt: i. e., thesealing surface to overcome this difiiculty. Hence, one of the objectsof the present invention is to provide a piston skirt which isimperforated and continuous so that for a given size cylinder andpercentage compressor efiiciency the length of the piston skirt may bedecreased, and still maintain the desired degree of compressorefficiency.

Another object is to provide a novel Wrist-pin carrier completelyenclosed within the piston skirt.

A further object is a new and improved means for rigidly securing thewrist-pin carrier within the piston.

A still further object is to produce a piston assembly for compressorscomprising a piston having a head portion which is slightly deformableoutwardly along the longitudinal axis of the piston when the wrist-pincarrier is forced into the piston skirt. The bulged piston head acts asa resilient force tending to continually urge the carrier upon aretainer member carried by the piston and thus the connection betweenthe piston and carrier will not become loose and noisy after longperiods of use.

Still another object is the provision of a light weight, sturdywrist-pin carrier.

The foregoing and other important objects and desirable featuresinherent in and encompassed by the invention, together with many of thepurposes and uses thereof, will become readily apparent from a readingof the ensuing description in conjunction with the annexed drawings, inwhich;

Figure 1 is a side elevational view showing the wrist-pin carrier andthe piston in cross-section;

Figure 2 is a view similar to Figure 1 and taken substantially alongline 2-2 of Figure 1;

Figure 3 is a perspective view in section of the piston assembly; and

Figure 4 is a plan sectional view taken substantially along the line 4-4of Figure 1.

Referring to the drawings, wherein like reference characters representlike elements throughout the various views, there is shown a connectingrod and piston assembly. The piston ID has a fiat head portion l I and ahollow cylindrical skirt portion or shell I2 integrally formed with thehead portion. The skirt portion [2 has at the end opposite the headportion ll, an internal annular groove I3.

A cross-shaped wrist-pin carrier I4 is adapted to be wholly disposedwithin the hollow cylindrical skirt portion l2 and rigidly secured tothe piston It. The wrist-pin carrier I4 has a hollow central portion l5and a plurality of circumferentially spaced radially disposed portionsor bosses l1, i8, i9, and 20 having their outer surfaces rounded orcontoured as shown at 2| to conform substantially to the contour of theinterior wall of the piston skirt portion I2. The wrist-pin carrier Hialso has a central raised portion I6 which has a diameter considerablyless than the internal diameter of the piston skirt portion [2. It willbe noted that two of the radially disposed portions l3 and 20 arediametrically opposed and provided with transversely aligned openings 22to define Wrist-pin bearing surfaces.

In assembly, the wrist-pin carrier [4 is advanced within the pistonskirt l2, applying a small amount of force until the raised portion I6is in direct physical contact with the underside of the piston headportion H. The piston head portion ll, being in the form of a flat platehaving its marginal edge secured, is slightly deformable.

When sufficient force is applied longitudinally to the wrist-pin carrierIt the piston head portion I I is bulged outwardly a very small amountsince the upward assembly force is concentrated about the center of thehead portion II. A resilient snap ring or retainer 24 is then slippedinto groove i3. The snap ring 24 provides an internally extending seatfor the lowermost surface of the wrist-pin carrier 14. By thisconstruction of the piston and wrist-pin carrier and the method ofassembly described above, the bulged piston head H which was stressedduring assembly acts as a resilient force tending to continually urgethe wrist-pin carrier [4 upon the ring 24. Thus, it will be apparentthat a very rigid piston assembly is produced which will not becomeloose and noisy even after long periods of use.

The embodiment of the invention chosen for the purposes of illustrationand description herein is that preferred for achieving the objects ofthe invention and developing the utility thereof in the most desirablemanner, due regard being had to existing factors of economy, simplicityof design, and the improvements sought to be expected. It will beappreciated, therefore, that the particular structural and functionalaspects emphasized herein are not intended to exclude but rather tosuggest such other adaptations and modifications as fall within thespirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A piston assembly comprising a piston having a relatively flat headportion when disassembled capable of being deformed when assembled, saidhead portion closing one end of an imperiorate cylindrical shell; ahollow wrist-pin carrier contained within said shell having a first pairof oppositely disposed portions contoured to conform to the interiorwall of said shell and a second pair of oppositely disposed portionsperpendicular to said first pair of portions, said second pair ofportions having transversely aligned openings to provide wrist-pinbearing surfaces said carrier having a central circular raised portion,said raised portion having an outer diameter less than the radius ofsaid head portion and being adapted to abut the underside of said headportion and bulge said head portion outwardly along the longitudinalaxis of said shell away from the open end of said shell whereby saidhead portion tends to flatten and move said carrier longitudinallytoward the open end of said shell; and retaining means engaging saidshell and carrier for preventing said head portion from completelyfiattening to rigidly secure said carrier to said piston.

2. A piston assembly comprising a piston having a normally flat headportion when disassembled capable of being deformed when assembled, saidhead portion closing one end of an imperforate cylindrical shell havingan internal annular groove located at the end opposite said headportion; a hollow wrist-pin carrier provided with wrist-pin. holes andhaving a central circular raised portion, said raised portion having anouter diameter less than the radius of said head portion and beingadapted to abut the underside of said head portion and bulge said headportion outwardly along the longitudinal axis of said shell whereby saidhead portion tends to flatten and assume its normal condition and movesaid carrier downwardly along the longitudinal axis of said shell; and aretainer comprising a split resiilent ring expanded into said groove andabutting the bottom surface of said carrier whereby said head portion isprevented from completely flattening and said carrier is rigidly heldbetween said retainer and said head portion.

3. A piston assembly comprising a piston having a fiat head portioncapable of being deformed, said head portion closing one end of animperiorate cylindrical shell having an internal annular groove locatedat the end opposite said head portion; a hollow wrist-pin carrier withinsaid shell having circumferentially spaced, diametrically opposed bossesabutting the interior surface of said shell, two of said bosses beingbored to provide wrist-pin bearings, said carrier having a central upperportion of smaller outer diameter than the internal diameter of saidshell adapted to abut the underside of said head portion and bulge saidhead portion outwardly along the longitudinal axis of said shell wherebysaid head portion is stressed and acts as a compressed spring and tendsto move said carrier downwardly along the longitudinal axis of saidshell; and a retainer comprising a split resilient ring expanded intosaid groove and abutting the bottom surface of said carrier whereby saidhead portion is maintained in its bulged condition and said carrier isrigidly held between said retainer and said head portion.

4. A piston assembly comprising a piston having a normally flat headportion when disassembled, said head portion being capable of beingdeformed when assembled, said head portion closing one end of animperforate cylindrical shell; a wrist-pin carrier provided withwrist-pin holes and having a central raised portion at one end thereofadapted to abut the underside of said head portion and bulge said headportion outwardly along the longitudinal axis of said shell away fromthe open end of said shell, the outer edge of said raised portionencircling an area which is less than one half of the total area of saidhead portion whereby said head portion tends to flatten and assume itsnormal condition and move said carrier downwardly along the longitudinalaxis of said shell toward the open end thereof; and means for engagingsaid shell and carrier adjacent the open end of said shell forpreventing said head portion from completely flattening to rigidlysecure said carrier to said piston.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,722,635 Knight July 30, 1929 FOREIGN PATENTS Number CountryDate 349,194 France Mar. 11, 190 277,759 Great Britain Sept. 26,, 1927

